答复: [PATCH] KVM: Clear pv eoi pending bit only when it is set

["Li,Rongqing" <lirongqing@baidu.com>]

> -----邮件原件-----
> 发件人: Paolo Bonzini <pbonzini@redhat.com>
> 发送时间: 2021年10月19日 15:29
> 收件人: Vitaly Kuznetsov <vkuznets@redhat.com>; Li,Rongqing
> <lirongqing@baidu.com>
> 抄送: seanjc@google.com; wanpengli@tencent.com; jmattson@google.com;
> joro@8bytes.org; tglx@linutronix.de; mingo@redhat.com; bp@alien8.de;
> x86@kernel.org; hpa@zytor.com; kvm@vger.kernel.org
> 主题: Re: [PATCH] KVM: Clear pv eoi pending bit only when it is set
> 
> On 19/10/21 09:23, Vitaly Kuznetsov wrote:
> >>
> >> -static void pv_eoi_clr_pending(struct kvm_vcpu *vcpu)
> >> +static void pv_eoi_clr_pending(struct kvm_vcpu *vcpu, bool pending)
> > Nitpick (and probably a matter of personal taste):
> > pv_eoi_clr_pending() has only one user and the change doesn't make its
> > interface much nicer, I'd suggest we just inline in instead. (we can
> > probably do the same to
> > pv_eoi_get_pending()/pv_eoi_set_pending() too).
> 
> Alternatively, merge pv_eoi_get_pending and pv_eoi_clr_pending into a single
> function pv_eoi_test_and_clear_pending, which returns the value of the
> pending bit.
> 
> So the caller can do essentially:
> 
> -	pending = pv_eoi_get_pending(vcpu);
> -	pv_eoi_clr_pending(vcpu);
> -	if (pending)
> +	if (pv_eoi_test_and_clear_pending(vcpu))
>                  return;
> 
> 

It is better to implement pv_eoi_test_and_clear_pending(), and it can fix the race that Vitaly suggested

And I will write a new function kvm_test_and_clear_bit_guest_cached, to be called in pv_eoi_test_and_clear_pending

Bool kvm_test_and_clear_bit_guest_cached（struct kvm_vcpu *vcpu，  struct gfn_to_hva_cache * ghc， long nr）

-Li 

> Paolo